Quan Chen

Mitochondria are bound by a double membrane and are semiautonomous organelles, rendering them highly vulnerable to global and internal proteostatic stress¹. Multiple surveillance mechanisms at proteostatic and inter-organellar levels have evolved to maintain mitochondrial integrity and cellular health^2,3,4,5,6,7. However, the precise mechanisms by which proteostatic damage relays stress signals across organelles and how the quality surveillance machinery coordinates these functions remain unknown. Here we report that under proteostatic stress, damaged mitochondrial proteins are sequestered to form stress-induced mitochondrial protein aggregates (SIMPAs) that activate specific quality control mechanisms in a spatially confined manner without perturbing the mitochondrial network. Quantitative proteomic and correlative light–electron microscopy analysis revealed that SIMPA mediates inter-organellar communication via mitochondria–endoplasmic reticulum contact sites or mitochondrial-associated membranes. Mechanistically, GRP75 coordinates SIMPA biogenesis and focally activates endoplasmic reticulum unfolded protein response pathways via mitochondria–endoplasmic reticulum contact sites or mitochondrial-associated membranes for the targeted clearance of SIMPAs. Functionally, in both cellular and liver disease models, we found that a GRP75-dependent SIMPA signalling cascade attenuates mitochondrial stress and preserves mitochondrial integrity under proteotoxic stress. Overall, we show that SIMPAs, functioning as protein condensates, serve as a central cross-compartment communication hub for mitochondrial quality control, supporting cellular and organismal fitness.

Aberrant innate immune responses contribute significantly to cellular senescence, yet the precise interplay between innate immunity and senescence remains poorly characterized. Here, we elucidate the pivotal role of nuclear respiratory factor 1 (NRF1) in orchestrating innate immune responses that drive senescence and the senescence-associated secretory phenotype (SASP). NRF1 deficiency delayed cellular senescence and ameliorated age-related deterioration in multiple organs. Mechanistically, NRF1 enhanced SASP by transcriptionally regulating TBK1 and IRF3, critical nodes in innate immunity essential for senescence induction. Conversely, NRF1 deficiency suppressed innate immune activation, thereby attenuating inflammation associated with senescence and aging. Additionally, DNA damage activated ATM kinase, which phosphorylated NRF1 at Ser393, augmenting the NRF1-TBK1/IRF3-type I interferon axis and exacerbating cellular senescence. Furthermore, NRF1 knockdown treatment effectively mitigated aging phenotypes and extended lifespan in aged mice. Collectively, our findings underscore the essential role of the ATM-NRF1-TBK1/IRF3-type I interferon axis in DNA damage-induced senescence, suggesting that targeted NRF1 modulation holds therapeutic promise for improving inflammaging.

The global surge in the population of people 60 years and older, including that in China, challenges healthcare systems with rising age‐related diseases. To address this demographic change, the Aging Biomarker Consortium (ABC) has launched the X-Age Project to develop a comprehensive aging evaluation system tailored to the Chinese population. Our goal is to identify robust biomarkers and construct composite aging clocks that capture biological age, defined as an individual’s physiological and molecular state, across diverse Chinese cohorts. This Perspective outlines the core objectives, methodological framework and key deliverables of the X-Age Project, including cohort recruitment, standardized sample collection, multimodal data acquisition and clock model development. By integrating interdisciplinary expertise, we aim to provide a practical and scalable platform for understanding aging complexity and heterogeneity, early detection of accelerated aging and evaluation of aging interventions.